Laser shock processing (LSP) is a typical non projectile impact surface strengthening technology, which can effectively improve the fatigue resistance, corrosion resistance, wear resistance and service life of metal materials. It has the advantages of high strain rate, high efficiency and good strengthening effect. In recent years, with the rapid development of aerospace and automobile manufacturing, the good property of weldments becomes more and more important. The excellent weld quality directly affects the qualification rate of weldments, and weld strengthening has always been a difficult challenge. Firstly, the principle of laser shock processing was introduced, and the parameters and conditions affecting laser shock processing were summarized, including laser power density, constraint layer and absorbing protective layer, laser shock times, spot overlap rate and laser pulse width. By controlling different strengthening process parameters, the microhardness of weld could be increased by 50%, the residual comprehensive stress could be increased by more than 65%, the tensile strength could be greatly improved and the fatigue crack propagation could be reduced. Then, the research and application of laser shock processing technology used by researchers in China and abroad were summarized to strengthen the welds of different materials, and the significant strengthening effect of laser shock processing on the mechanical properties and microstructure of the weld was discussed in particular. By controlling the combination of different shock strengthening process parameters, the process effect could be improved. Compared with the unstrengthened samples, the properties of strengthened samples were significantly improved. In terms of mechanical properties, the changes of microhardness, residual stress and fatigue crack propagation were analyzed in detail, and the reasons for different changes of microhardness of aluminum alloy were expounded. The experimental effects of strengthening in weld zone, heat affected zone and base metal zone were compared and introduced. It was found that the microhardness could be increased by 20%-80%. Combined with the theoretical research, simulation analysis and experimental synchronous demonstration of residual stress, it is considered that laser shock processing can effectively control the fatigue crack growth and improve the fatigue life by increasing the residual stress, but the coupling of many factors makes the crack growth uncertain, which can be discussed through orthogonal test to obtain the best parameter combination. By analyzing the microstructure changes after laser shock processing, it is considered that laser shock processing can transform the grains into equiaxed grains through twinning, resulting in dislocation substructure and a large amount of deformation as well as grain refinement. Grain refinement can slow down the crack propagation and prevent the occurrence of cracks. Therefore, the mechanism of laser shock strengthening grain refinement is obtained. Under the synergistic effect of different laser shock processing parameters, the microstructure evolution such as dynamic recrystallization and grain refinement and dislocation movement can increase the residual stress and hardness, resulting in the interaction between mechanical properties and microstructure. It is considered that laser shock processing technology is an effective post welding treatment process for weld strengthening. Finally, the application prospect of laser shock processing technology in the field of weld strengthening is prospected. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.
